Specifications for a 1998 Yamaha YZ125

by Rob Wagner

The 1998 Yamaha YZ 125 motorcycle was produced by the Japan-based Yamaha Corporation. The bike is part of the YZ 125 family that has been in production since 1974 and is designed specifically for motocross racing. A perennial winner in motocross and supercross championship racing, the Yamaha YZ 125 is regarded as one of the best dirt bikes ever produced. Its siblings are the YZ 400F, the YZ 250 and the YZ 80.


Yamaha began production of its YZ 125 in 1974 and made very few changes to the model over the years. By 1996, the model was considered the standard in lightweight motocross bikes. Motocross magazines beginning in 1996 consistently gave it top marks in handling and power in its class. The 1998 YZS 125 is generally regarded as the best model due to a number of enhancements in suspension and braking, according to Motorsports-Network.com.


The 1998 YZ 125 is powered by a two-stroke liquid-cooled, single-carburetor 124cc engine. It features a 1.85-inch bore and 1.88-inch stroke with a compression ratio of 8.9:1.The engine generates 37.38 horsepower and 18.14 foot-pounds of torque. Torque is the twisting force generated inside the engine to give the bike quick acceleration. Electrical power is provided by a standard 12-volt battery; the ignition is a kick-start. The engine is matched with a constant mesh six-speed transmission and chain drive.


The wheelbase of the Yamaha YZ 125 is 56.9 inches long, with the chassis’ overall length at 84.2 inches. Seat height measures 39.2 inches from the ground, with overall height of the bike at 51.7 inches (ground to top of the handlebars). Ground clearance is a relatively high 15.7 inches with the telescopic front fork measuring 11.81 inches, and the swing arm rear suspension featuring 12.4 inches of travel. Front and rear shock absorbers are coil springs. The YZ 125’s dry weight is 196 lbs.

Stopping Power

Front and rear brakes employ a single disc brake with the front brake diameter measuring 9.64 inches and the rear disc brake at 9.44 inches. Both wheels are made of cast aluminum with the front tire measuring 1.60 by 21 inches and the rear at 1.81 by 19 inches.

Performance and Cost

The 1998 Yamaha YZ 125’s performance outshined earlier models because of the “Works-style” Kayaba front forks that give it a longer stroke before bottoming out to allow the rider to traverse even the worst off-road track conditions at maximum speed. The bike was tested by leading motocross magazines and was found to have precise handling, especially in braking that was sensitive to the touch when applied in sliding turns. The bike is available only in a Team Yamaha blue and white color scheme. It sold for $4,799.

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